This invention relates generally to sewing machine gauges and, more particularly, to a gauge having provisions incorporated therein to enable an individual to continuously monitor the condition of the thread contained on a bobbin disposed below the gauge.
In conventional sewing machines, two supplies of thread must necessarily be provided. One of these is the thread supplying the needle itself which is usually in the form of a spool located on the upper portion of the machine and in plain view of the operator, thus allowing the operator to continuously monitor the amount of thread remaining, as well as the condition of the thread as it passes through various tensioning and other feed control devices. Thus, should this thread become snagged upon a portion of the machine or should the supply become exhausted, the operator will be immediately aware of the problem which may then be easily corrected.
The second supply of thread required on such machines is generally located in a bobbin case disposed in the lower portion of the machine, normally immediately adjacent to and below the needle. In normal operation, this bobbin case is concealed from view by a cover member or throat plate. Thus, the operator of the machine must either guess as to the condition and amount of thread remaining on the bobbin or go through the time consuming process of periodically removing the throat plate thereby exposing the bobbin for a visual inspection. This arrangement is particularly undesirable on machines being used for commercial operations, as it will likely result in bobbins being replaced before the thread supply is exhausted thus wasting materials in addition to reducing the output available from the machine and operator thereof as the operator must periodically cease production to inspect the condition of the bobbin thread supply. Should the operator continue sewing after the thread supply from the bobbin has been exhausted or otherwise interrupted, the stitches will not hold and thus it will be necessary to spend additional time removing the unsecured stitches and restitching the entire article thus consuming substantial time, reducing the machine and operator's output and otherwise delaying production. Additionally, when sewing certain types of materials, it will be impossible to go back and restitch the material should the bobbin thread become broken or the supply be exhausted during a stitching operation, as the initial needle punctures will remain visible thus incurring additional costs in the form of wasted material.
While such problems may be annoying to the homemaker doing only occasional sewing, they are extremely significant in high volume production work. It is estimated that a single production line seamstress will completely exhaust 50 bobbins during an 8 hour shift. That means that a single operator will be using approximately 6 bobbins an hour. When this figure is multiplied by numerous operators, it is apparent that substantial amounts of time, money, and materials may be wasted due to the inability to continuously monitor the bobbin thread supply and condition.
Various attempts have been made to provide a solution to this problem by providing assorted arrangements of apertures, lights, mirrors, and other devices designed to inform the operator of the bobbin thread condition. However, none of these arrangements have been totally acceptable.
In one arrangement, transparent plexiglass throat plates were designed to replace the typical metal plates. This arrangement worked quite well initially, but as material was continuously moved across the throat plate, the plexiglass became scratched and clouded thereby requiring frequent machine down time in order to replace them and rendering their usefulness over an extended time period uneconomical. Also when a stitch depth gauge was installed on the machine, it concealed the view of the bobbin. As such stitch depth gauges are commonly used in producting sewing, this device proved totally unsuitable for such applications.
Another arrangement provides a remotely located opening in combination with mirrors to enable the operator to view the bobbin. While this arrangement eliminates the problems associated with the transparent throat plate, it is expensive to install and requires the mirrors be readjusted for different operators thus making them costly to use on a production line basis. Additionally, the mirrors require cleaning periodically and are subject to breakage.
Accordingly, the present invention offers a unique solution to this problem in providing means by which the machine operator may easily continuously visually inspect the condition of the bobbin thread, the supply remaining on the bobbin, as well as observing the operation of bobbin stitching mechanisms. The present invention provides a stitching gauge which is specially adapted to include a window portion therein which cooperates with an opening provided in the throat plate to afford the operator an unobstructed view of the bobbin thread and associated feed mechanism. The device thus provided may be easily adapted to fit most any conventional home or industrial sewing machine and is extremely durable while still affording means for easily adjusting the stitch gauge for any particular job. As the material being sewn does not pass across the window, the device is extremely rugged and may be inexpensively fabricated the problems associated with these prior arrangements are effectively overcome. Further, the window may be adapted to be easily and quickly cleaned and/or replaced should it become damaged or broken thus minimizing machine down time while affording substantial savings in material costs and increasing operator productivity.
Additional features and advantages of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.